From the very beginning, security has played an integral role in the world of aeronautics. Aircraft manufacturers and airlines have progressively developed and integrated a certain number of operations aiming at improving safety onboard aircraft.
From the aircraft manufacturer's point of view, armoured cockpit doors, video-surveillance inside the airplane, or even the protection of information systems on-board against possible computer hacking operations can be cited in particular.
Airlines have taken a certain number of measures such as, for example, the presence of a sky marshal on-board, the training of personnel consisting of learning how to manage aircraft hijacking or even provisions for the safety of the aircraft on the ground. These provisions consist in particular of ensuring that the airplane is intact after having spent a night outside of its base: the external hatches, doors and maintenance panels must be checked in order to determine if anyone has entered the airplane during the night or if they have placed a bomb inside the airplane. There are numerous methods which enable the integrity of the airplane to be verified, in particular:                pelletizing, which consists of placing seals on all of the external openings in the evening, after the disembarkation of passengers and personnel; the following day, someone in charge of the ground security checks the condition of these seals, however this method is fastidious and above all unreliable, as these seals can be fairly easily replaced without any visible indications;        the on-board video-surveillance, adapted to particular situations and using a set of cameras as well as a detection device by radar and/or infrared sensors; this method being described in more detail below.        
The airplanes are, in certain cases, parked in areas where monitoring is tricky or even difficult; security, very expensive, can even be completely inefficient. In this last example, the best solution remains video-surveillance.
The best solution for video-surveillance to be present in all of the airports where the airplane is stopping, is to have at least one camera on the external surface of the airplane's fuselage.
Conventionally, there exists a POD-type container which fulfils the video-surveillance of an airplane function. The POD is a container attached to the underside of an apparatus in order to place different devices on the apparatus, such as, for example, cameras.
FIGS. 1 and 2 represent such a device; FIG. 3 shows the different view points taken from such a POD; FIG. 4 represents an overall view of the airplane considered.
FIG. 1 shows an overall close-up view of a POD 100 installed on belly fairing 103 of the airplane. POD 100 includes in particular:                a set of four infrared-type cameras 101A, 101B, 101C and 101D placed in such a way that their central axes are perpendicular to each other and parallel to the plane defined by the floor, with the purpose of having a horizontal line of vision, 360 degrees around the airplane; as a result, cameras 101C and 101D are not visible on this view from the perspective of POD 100.        a radar 102 placed in its centre, capable of detecting movements near airplane 102.        
In other modes of embodiment of this device, infrared sensors detect movements in the dark. The radar and/or sensors order cameras 101A, 101B, 101C and 101D to start a video recording when they detect movements near airplane 102.
FIG. 2 shows an overall distant view of POD 100 installed on belly fairing 103 of the airplane.
FIG. 3 shows the four view points 300A, 300B, 300C and 300D captured by cameras 101A, 101B, 101C and 101D, respectively. The central axis of camera 101A is orientated towards the front part of the airplane. The central axis of camera 101B is orientated towards the left-hand wing of the airplane. The central axis of camera 101C, not represented on FIG. 1 but represented on FIG. 4, is orientated towards the rear part of the airplane. The central axis of camera 101D, not represented on FIG. 1 but represented on FIG. 4, is orientated towards the right-hand wing of the airplane.
FIG. 4 represents an overall aerial view of the airplane equipped with POD 100. The airplane considered is in the center of a security perimeter 401, circular in shape. When an individual 402 intrudes 403 in secured area 401, radar 102 detects a movement 404, which activates the video recording of cameras 101A, 101B, 101C and 101D, and simultaneously triggers the sending of an alarm message 405 to a security station 406.
This type of video-surveillance is suitable for situations where there is very little traffic around the aircraft. A major problem therefore occurs when the airplane stops over in a large airport where numerous people are circulating: all of the persons penetrating security perimeter 401 activate an alarm, even though the majority have authorization to do so, which generates a large quantity of information which is difficult to analyze.